Some known rotary valves include a housing and a ball supported for rotation in a chamber in the housing. Rotation of the ball in the housing, through rotary force applied to a valve stem, controls fluid flow through the valve. A packing is interposed between the ball and the housing to help seal the chamber. A stack of Belleville springs, between a top gland and a bottom gland, exerts a force (a “live load”) on the packing. The stack of springs is secured in the housing by a packing bolt that is screwed into the housing. The springs maintain load on the packing and thus can compensate for material creep in the valve and temperature variations.
Setting the proper load on the springs can be important to ensure proper functioning and life of the valve. The packing bolt needs to be screwed in by the proper amount so that a specific and accurate load is applied to the springs and thus to the packing, to create an optimal seal for thermal cycle capability and room temperature cycle life.
The proper load setting has been achieved in the past by screwing the packing bolt in until it contacts the top gland, then rotating the bolt a predetermined number of degrees. Another way the proper load setting has been achieved is by screwing the bolt in until it contacts the top gland, then rotating the bolt until it moves axially by a predetermined distance after it contacts the top gland. Although these methods work, they are dependent on human interaction to find the starting point where the bolt first makes contact. As a result, these methods are not easily amenable to cost effective process control in a production environment. The present invention addresses these needs.